This invention is related generally to field emitter devices and field emitter arrays incorporating such devices.
Field emitter arrays (FEAs) generally include an array of field emitter devices. Each emitter device, when properly driven, can emit electrons from the tip of the device. Field emitter arrays have many applications, one of which is in field emitter displays (FEDs), which can be implemented as a flat panel display.
FIG. 1 illustrates a portion of a conventional Field Emitter Device. The field emitter device 1 shown in FIG. 1 is often referred to as a “Spindt-type” FEA. It includes a field emitter tip 12 formed on a semiconductor substrate 10. Refractory metal, carbide, diamond and silicon tips, silicon carbon nanotubes and metallic nanowires are some of the structures known to be used as field emitter tips 12. The field emitter tip 12 is adjacent to an insulating layer 14 and a conducting gate layer 16. By applying an appropriate voltage to the conducting gate layer 16, the current to the field emitter tip 12 passing through semiconductor substrate 10 is controlled.
FEAs typically operate in very high vacuums (often better than 10−8 Torr for Spindt types and nanowires and 10−7 Torr for nanotubes). This is because the gate voltages required to generate field emitted currents are also sufficient to produce an arc discharge between the gate and emitting tip at higher pressure levels consistent with other low vacuum electronic products. The vacuum requirements limit the number of FEA applications to those employing expensive high vacuum systems. The FEAs must also be handled with extreme care, often in clean rooms, because a simple dust particle can short out the gate—emitter circuit and destroy the device.
Thus, prior art FEAs, either those based on refractory metal tips or nanotubes or nanowires, are prone to arcing, and require good vacuums (10−7 Torr or better) for operation. Further, prior art FEAs are sensitive to contamination by dust, skin oils etc. which can short out the devices. These requirements make prior art FEAs both difficult to handle and to utilize.